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Publication numberUS5073588 A
Publication typeGrant
Application numberUS 07/238,703
Publication dateDec 17, 1991
Filing dateAug 31, 1988
Priority dateAug 31, 1987
Fee statusLapsed
Also published asDE3729039A1, EP0305838A1, EP0305838B1
Publication number07238703, 238703, US 5073588 A, US 5073588A, US-A-5073588, US5073588 A, US5073588A
InventorsHans-Guenter Seltmann, Juergen Haerer, Hans-Josef Hoffmann
Original AssigneeHenkel Kommanditgesellschaft Auf Aktien
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Glycidoxypropyl silanol and polydimethyl siloxanes as mold release agents
US 5073588 A
Abstract
An aqueous solution of suspension of glycidoxypropyl silanol and polydimethyl siloxanes having a number average molecular wieght of more than 100,000 and their use as mold release agents with good release values over a relatively large number of molding cycles in the molding of rubber and plastics.
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Claims(3)
We claim:
1. A mold release composition substantially free from organic solvents in the form of an aqueous emulsion, solution, or suspension comprising
A. from about 0.5 to about 3% by weight of glycidoxypropyl silanol, and
B from about 0.2 to about 2% by weight of an aqueous silicone latex containing from about 25 to about 55% by weight of a polydimethyl siloxane having a number average molecular weight of more than 100,000.
2. A method of coating a mold with a mold release agent comprising applying to the mold the mold release composition of claim 1 and carrying out at least ten molding cycles before reapplying said mold release composition to the mold.
3. The method of claim 2 wherein the mold is a mold for rubber or plastics.
Description
BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to aqueous solutions or suspensions containing glycidoxypropyl silanol and polydimethyl siloxanes having a number average molecular weight or more than 100,000 as mold release agents for plastics.

2. Statement of Related Art

Various mold release agents containing the following substances are known and are commercially available:

1. water-soluble surfactants;

2. silicone oils containing organic solvents;

3. crosslinkable silicone resins containing organic solvents, and

4. silicone latices.

In addition to certain advantages however, the mold release agents disclosed above also show serious disadvantages. Thus, although they show ready biodegradability and produce a good release effect, the mold release agents of group 1 are stripped from the mold during each release cycle. To produce a thin film on the mold, the mold release agents of group 2 have to be dissolved in organic solvents. Since these solvents are inflammable and since the mold release agents are applied to molds heated to around 160 C., they can only be used in explosion-proof plants. If, on the other hand, non-inflammable halogenated hydrocarbons are used as the solvents, the usual disposal measures have to be taken due to the solvent vapors formed. The mold release agents of group 2 also have to be re-applied after each cycle. In addition, they remain behind on the surfaces of the molding which therefore have to be cleaned before lacquering.

The mold release agents of group 3 have the disadvantages already mentioned due to the presence of solvents in them, although they do remain in place for several molding cycles. Although the mold release agents of group 4 are free from organic solvents, they are also easily stripped so that they often have to be re-applied and, in addition, cause soiling of the mold in practice. Accordingly, there is a need for mold release agents which are free from organic solvents and which do not have to be replaced for at least several molding cycles.

DESCRIPTION OF THE INVENTION

Other than in the operating examples, or where otherwise indicated, all numbers expressing quantities of ingredients or reaction conditions used herein are to be understood as modified in all instances by the term "about".

It has now been found that aqueous emulsions, solutions, or suspensions containing glycidoxypropyl silanol and polydimethyl siloxanes having a number average molecular weight of more than 100,000, which are free from organic solvents, do not have to be replaced until after ten or more molding cycles. Apart from traces of alcohol formed during hydrolysis, the solutions or suspensions to be used in accordance with the invention contain only water as solvent, form a stripping-resistant, effectively releasing film in the mold, which withstands a number of vulcanization cycles, and does not adhere to the surface of the moldings, so that there is no need for cleaning before lacquering or bonding. The molds treated with the mold release compositions of the invention are preferably molds for rubber or plastics.

The present invention also relates to a mold release agent containing 0.5 to 3% by weight glycidoxypropyl silanol and 0.2 to 2% by weight of a silicone latex, the silicone latex containing approximately 25 to 55% by weight of a polydimethyl siloxane having a number average molecular weight of more than 100,000 in aqueous emulsion, in aqueous solution, or in suspension.

The glycidoxypropyl silanol used in accordance with the invention is a known compound which can be obtained by hydrolysis of commercial 3-glycidoxypropyl trimethoxy or triethoxy silane with dilute acids, preferably acetic acid, at pH values of 4 to 4.5. In addition to the glycidoxypropyl silanol, the hydrolysis product may contain other hydrolysis products (through ring opening of the epoxide group) and condensates (through reactions at the silanol group). Silicone latices for use in accordance with the invention are commercially available compounds.

The invention is illustrated but not limited by the following Examples and Comparison Examples.

EXAMPLES EXAMPLE 1 (a) Preparation of Glycidoxypropyl Silanol:

In a three-necked flask equipped with a stirrer, dropping funnel and reflux condenser, 500 g water were adjusted with dilute acetic acid to a pH value of 4 to 4.5. 15 g glycidoxypropyl triethoxysilane were then added dropwise, the mixture being heated to 90 C. This temperature was maintained for 1 hour.

(b) Preparation of the Release Agent

The cooled silanol solution obtained in step a) was mixed while stirring with 6,5 g of a polydimethyl siloxane latex having the following properties: anionically stabilized emulsion, number average molecular weight of the polydimethyl siloxane above 100,000, content of non-volatile constituents 40% by weight, specific gravity 1.02, pH value 11.2, viscosity 1000 cps. The product is commercially available.

EXAMPLE 2

A mold release agent containing 3% by weight glycidoxypropyl silanol and 1% by weight silicone latex was prepared in the same way as described in Example 1.

EXAMPLE 3

A mold release agent containing 1.3% by weight glycidoxypropyl silanol and 0.22% by weight silicone latex was prepared in the same way as described in Example 1.

The test mold used was a construction comprising an upper circular plate 85 mm in diameter provided with 16 M12 hexagonal screws, a lower circular plate formed with grooves into which the rubber was pressed and a rubber blank arranged between the two circular plates. A rubber mixture having the following composition was used:

______________________________________SBR                100    parts by weightStearic acid       1      part by weightZnO                10     parts by weightAntiager           1      part by weightParaffin (42-44 C.)              1      part by weightHAF carbon black   70     parts by weightAccelerator        1      part by weightSulfur             0.8    part by weight______________________________________

The vulcanization conditions were as follows:

______________________________________Vulcanization temperature:                  170 C.Vulcanization time:     7 minutesPressure:              150 bar______________________________________

To carry out the release tests, the release agent was sprayed onto the mold described above and baked for 30 minutes at 150 C. The rubber blank was then molded.

The upper and lower circular plates were vertically released in a tensile testing machine. The maximum release values were recorded. Further molding and release cycles were then carried out with no re-application of release agents.

The results obtained with the release agents according to Examples 1 to 3 are shown in the Table at the end of the Examples.

In addition, comparison tests I to VIII were carried out under the conditions described above, the following compositions being tested:

I : without release agent

II : solvent-containing silicone resin (commercially available)

III : 1% surfactant (alkane sulfonate) in water (commercially available)

IV : 1% of the silicone latex used in Example 1

V : 3% of the glycidoxypropyl silanol used in Example 1

VI : 3% hydrolyzed aminoethyl aminopropyl triethoxysilane (commercially available)

VII : 5% Y-aminopropyl triethoxysilane

VIII : 3% hydrolyzed vinyl triethoxysilane

Mixtures of the silicone latex of Example 1 with the hydrolyzed silanes of Comparison Examples VI, VII and VIII were not stable and, accordingly, did not produce useful mold release agents.

The results of the comparison tests are also shown in the Table at the end of the Examples.

It can be seen from the Table that the mold release agents of Examples 1 to 3 according to the invention produce an excellent release effect, even in the 1Oth molding cycle. Compared with the individual components (comparison tests IV and V), highly enhanced effects were obtained with the combinations according to the invention. Finally, the release agents according to the invention have the advantage over Comparison Example II in that they contain no solvents.

              TABLE______________________________________(Release values in N)  1st release          2nd release                    5th release                              10th release  value   value     value     value______________________________________Example1        7         6         7       72        12        15        17      203        7         7         8       8ComparisonExampleI        45        45        45      45II       9         9         8.5     9III      8         12        20      40IV       8         11        15      25V        40        35        17      15VI       16        20        35      45VII      45        45        45      45VIII     45        45        45      45______________________________________
Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3485780 *Mar 18, 1968Dec 23, 1969Union Carbide CorpRoom temperature vulcanizable siloxane compositions and the elastomers derived therefrom
US3872038 *Dec 3, 1973Mar 18, 1975Stauffer Chemical CoAqueous based release composition
US4677160 *Apr 9, 1986Jun 30, 1987Toray Silicone Co., Ltd.Blend with colloidal silica, or alkali metal sili agent, emulsifier and coupling agent
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5728339 *Feb 14, 1996Mar 17, 1998Hoechst Celanese CorporationIn-line silicone coated polyester film and a process for coating the film
US7520742 *Mar 17, 2004Apr 21, 2009Hitachi, Ltd.Nanoprint equipment and method of making fine structure
Classifications
U.S. Classification524/264, 524/265, 264/331.11, 427/387
International ClassificationC09D183/04, B29C33/64
Cooperative ClassificationC09D183/04, B29C33/64
European ClassificationC09D183/04, B29C33/64
Legal Events
DateCodeEventDescription
Feb 20, 1996FPExpired due to failure to pay maintenance fee
Effective date: 19951220
Dec 17, 1995LAPSLapse for failure to pay maintenance fees
Jul 25, 1995REMIMaintenance fee reminder mailed
Nov 7, 1988ASAssignment
Owner name: HENKEL KOMMANDITGESELLSCHAFT AUF AKTIEN (HENKEL KG
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNORS:SELTMANN, HANS-GUENTER;HAERER, JUERGEN;HOFFMANN, HANS-JOSEF;REEL/FRAME:004983/0121
Effective date: 19880831
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:SELTMANN, HANS-GUENTER;HAERER, JUERGEN;HOFFMANN, HANS-JOSEF;REEL/FRAME:004983/0121